GGCX mutants that impair hemostasis reveal the importance of processivity and full carboxylation to VKD protein function.

γ-Glutamyl carboxylase (GGCX) generates multiple carboxylated Glus (Glas) in vitamin K-dependent (VKD) proteins that are required for their functions. GGCX is processive, remaining bound to VKD proteins throughout multiple Glu carboxylations, and this study reveals the essentiality of processivity to VKD protein function. GGCX mutants (V255M and S300F) whose combined heterozygosity in a patient causes defective clotting and calcification were studied using a novel assay that mimics in vivo carboxylation.

Streptavidin cooperative allosterism upon binding biotin observed by differential changes in intrinsic fluorescence.

While the binding of biotin by streptavidin does not appear to be cooperative in the traditional sense of altered binding strength, it has been suggested that it may be cooperative in terms of differential structural changes in the protein. In this work we present intrinsic tryptophan fluorescence data as evidence of a cooperative structural change. The technique involves examination of the differences in fluorescence emission corresponding to distinct tryptophan populations accompanying protein-ligand binding.

Biochemical defects in minor spliceosome function in the developmental disorder MOPD I.

Biallelic mutations of the human RNU4ATAC gene, which codes for the minor spliceosomal U4atac snRNA, cause the developmental disorder, MOPD I/TALS. To date, nine separate mutations in RNU4ATAC have been identified in MOPD I patients. Evidence suggests that all of these mutations lead to abrogation of U4atac snRNA function and impaired minor intron splicing.